Have we ever considered adding a tag/field to the database where Mods can officially note a film is Lost?
We consider and discuss what to do with lost films every couple of years, and the general decision ends up as: trying to remove/exclude them ends up leading to more issues than it solves. We have at times come up with potential compromises that could improve things (such as your suggestion of a tag that would leave the film on the list but not counting towards the total), but those would require adding features and db fields which is quite a bit of work.
Well then, I won’t be surprised when other (potentially) lost films appear on the new most favorited lists. Clearly if a film with two favorites (and 67 checks) is able to make a Top 100, then the bar isn’t very high.